Messages in this thread | | | Date | Sun, 13 May 2012 10:55:28 +0200 | Subject | Re: BUG: jbd2 slowing down file copies even though no journaling file system is used | From | Björn Christoph <> |
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Ted,
dm-1 points to my Linux-OS partition which is actually the encrypted LVM one. However, I could also see that on some copies this actually points to the related truecrypt partition so that makes sense there (the dm-1 doesn't imo but not important at this point).
"echo 1 > /sys/kernel/debug/tracing/events/ext4/ext4_sync_file_enter/enable" didn't work for me, I got a "permission denied" error. So then I figured out I have to use "sudo -i" to get a root shell, then I can actually echo into that file ? Very strange but an Ubuntu issue/feature I guess.
However, I don't see that the file /sys/kernel/debug/tracing/trace changes a lot? All I see is this even though I am clearly copying data onto the disk via samba:
# tracer: nop # # TASK-PID CPU# TIMESTAMP FUNCTION # | | | | | <...>-2096 [001] 1111.151516: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 1 <...>-2096 [000] 1111.201520: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 0 <...>-2096 [001] 1111.252939: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 1 <...>-2096 [000] 1111.290241: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 0 <...>-2096 [001] 1111.341757: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 1 <...>-2096 [000] 1111.367540: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 0 <...>-2096 [001] 1111.419511: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 1 <...>-2096 [000] 1111.456354: ext4_sync_file_enter: dev 252,1 ino 3410181 parent 3410196 datasync 0
PID 2096 is sshd acc. to "top" (I think this was my local copying to a file from /dev/zero?).
Even if I copy data now, the file never changes, I always see the same "cat" output?
I changed the entry back to 0, rebooted, changed it back to 1, started copying a file to an ext4 partition and cat /sys/kernel/debug/tracing/trace is just plain empty (shows "tracer: nop", TASK-PID etc but no data).
I'm a bit lost on how to gather the required traces :(
Thanks and regards, Bjoern
2012/5/13 Ted Ts'o <tytso@mit.edu>: > On Sun, May 13, 2012 at 01:21:00AM +0200, Björn Christoph wrote: >> >> IOTOP shows this in some cases, mostly jbd2 is not there: >> PRIO USER DISK READ DISK WRITE SWAPIN IO> COMMAND >> 416 be/3 root 0.00 B/s 97.65 M/s 0.00 % 13.74 % [jbd2/dm-1-8] > > Well, the file system in that has the huge write bandwidth is > whichever device is associated with device mapper device dm-1 (i.e., > with a device mapper minor number of 1). What does "ls -l > /dev/mapper" show you? > > Whatever file system is associated with it is clearly generating a lot > of journal activity. > > Something that may help in determining what process is generating all > of this journal activity (which is likely the result of something > calling fsync a lot) is to try this: > > echo 1 > /sys/kernel/debug/tracing/events/ext4/ext4_sync_file_enter/enable > > ... then wait for a minute or so, and then capture the output of: > > cat /sys/kernel/debug/tracing/trace > > See if that shows up anything useful. > > Regards, > > - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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